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Linzer biol. Beitr. 32/2 1291-1299 30.11.2000

The genus Neptosternus SHARP 1882 in the Philippines: and Biogeography (Coleoptera: )

L. HENDRICH & M. BALKE

Abstract: Two new species of rheobiont diving are here described from the Philippines: Neptosternus cebuensis sp.n. [Cebu] and N. montalbanensis sp.n. [Luzon]. Together with N. hydaticoides (REGIMBART 1877), a total of three Neptosternus species are now known from the Philippines. Neptosternus cebuensis sp.n. is a rather distinct species, while N. montalbanensis sp.n. appears close to N. chumphon BALKE & HENDRICH 1998 [Thailand]. The distribution of Neptosternus species in the Philippines is illustrated here, and we briefly outline biogeographical patterns in southeast Asian Neptosternus.

Key words: Coleoptera, Dytiscidae, Neptosternus, new species, Philippines, Biogeography.

Introduction

Species of the laccophiline genus Neptosternus SHARP 1882 are confined to the Afrotro- pical and Oriental regions. The genus currently comprises 84 species. Southeast Asian representatives were most recently revised by HENDRICH & BALKE (1997). The fauna of that region had to be updated soon afterwards, again indicating the remarkable species diversity of Nepstostemus (BALKE et al. 1997; BALKE & HENDRICH 1998; this paper). 56 species in total are now known from SE Asia. The present paper is in part based on historical material which was collected in the Philippines at the beginning of the last century and sold by the traders Bang Haas & Staudinger (Dresden, Germany) to the French coleopterist Raymond Peschet [1880- 1940]. Recently, several specimens were collected on various islands of the Philippines by Dr Herbert Zettel (NMW, Austria) and Dr. Jan Kodada (Bratislava, Slovakic Repu- blic). The collected by H. Zettel are the result of fieldwork conducted in the course of the Philippine water bug project (see: Annalen des Naturhistorischen Museum Wien 101B: 33-161 [several authors]). Besides Neptosternus hydaticoides (REGIMBART 1877), we recognized two undescribed species among the material studied. Here, we describe these new species, rising the num- ber of known Philippine Neptosternus species to three. © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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Material and Methods

Specimens mentioned in this work are deposited in several collections which are abbre- viated in the text as follows: CBH Collection Michael Balke and Lars Hendrich, Berlin, Germany CHZ Collection Herbert Zettel, Vienna, Austria LBMH Museum of Natural History, University of the Philippines, Los Banos, Philippines MNHN Museum National d'Histoire Naturelle, Paris, France NMW Naturhistorisches Museum Wien, Austria ZSM Zoologische Staatssammlung München, Germany Habitus drawings were made with a drawing tube attached to a Leitz MZ12, the median lobes were traced from SEMs. The style of the descriptive notes follows HENDRICH & BALKE (1995), BALKE et al. (1997), BALKE & HENDRICH (1998), and HENDRICH & BALKE (1999).

Taxonomy

The genus Neptosternus SHARP is characterized by two apomorphies: Prosternal process trifid (plesiomorphic character state: simple, with only one tip); and posterior angle of pronotum greatly produced backwards, needle-shaped and acute (plesiomorphic character state: not produced backwards, rounded). The following three species are now known from the Philippines (Fig. 9):

N. cebuensis sp.n. Philippines: Cebu N. hydaticides (REGIMBART 1877) South East Asia, Philippines N. montalbanensis sp.n. Philippines: Luzon

Neptosternus cebuensis sp. n. H o 1 o t y p e : 6: "Philippinen: Cebu, S Badian / Matutinao, Kawasan Falls / 250m, 23.-24.2.1997 / leg. H. Zettel (116)" (LBMH). 1 $ Paratype with same locality data (CHZ). Etymology: Named after the type locality. Description: Measurements (N = 2). Total length of holotype 3,20 mm; length without head 2,85 mm; greatest width of beetle 1,75 mm. Total length of paratype 3,20 mm; length without head 2,80 mm; greatest width of beetle 1,70 mm. Diagnosis: Small, somewhat broadly-elongate species with broad yellow subbasal band on elytron and an anteriorly and posteriorly darkened pronotum; body slightly arched in lateral view. Elytron with fine punctation only, lacking large discal punctures. Colour: Upper side dark with large yellow patches. Head ferrugineous; anteriorly ferrugineous or darker, castaneous. Pronotum medially yellowish; anteriorly and poste- riorly dark, blackish. Elytron blackish with two major yellow areas: a broad subbasal band; and a median-submarginal patch that is marginally fused with the apical patch (Fig. 1). Subbasal band and median-submarginal patch both reaching the margin of the elytron. On the holotype, a small, indistinct reddish patch is visible medio-discally but only on the © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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Neptosternus hydaticoides (REGIMBART 1877) Laccopilus hydaticoides REGIMBART 1877: 359. Neptosternus hydaticoides (REGIMBART): REGIMBART 1899: 270; HENDRICH & BALKE 1997: 57- 58, and references therein. H o 1 o t y p e : 6: "[Philippinen] Manille, Baer" (MNHN) (studied by HENDRICH & BALKE 1997). Additional material examined:! ex.: Philippines: Negros, Lousiana, Banks leg. [probably mislabeled, the only locality in the Philippines named "Luisiana" is situated on Luzon] (ZSM); 1 ex.: Mindanao, Surigao, Baker leg. (ZSM); 3 ex.: Mindanao, Misambis occ, W Ozamiz, Tangub, Lumban, 6.iii.l997, H. Zettel leg. (124); 2 ex.: Mindanao, Zamboanga d.S., 14 km N Pagadian, Datagan, Kendis cave, 10.iii.1997, H. Zettel leg. (127); 7 ex.: Luzon, Montalba, Coll. Peschet (MNHN); 4 ex.: Mindoro, 28 km S Calapan, Balete (18), 100-700m, 27.- 29.11.1992, H. Zettel leg. (CBH, NMW); 4 ex.: Ticao Island, Monreal, real, Matang Tubig spring, 28.2.1998, H. Zettel leg. (151) (NMW); 1 ex.: Palawan, 9 km W P. Princess Iwahig, 7.- 8.4.1994, Zettel leg. (CBH, NMW); 4 ex.: C-Palawan, Umg. Cabanyugan, 100 m 2.12.1995, J. Kodada leg. (CBH, NMW); 2 ex.: Zambales, Olongapo, Subic Base, JEST (Jungle Surv.), 4.XÜ.1993, H. Zettel leg. (37h). Description: Measurements (N = 5). Total length of beetle 3,25-3,30 mm; length without head 3,00-3,10 mm; greatest width of beetle 1,75-1,85 mm. Diagnosis: Medium-sized, elongate species, usually with five yellows patches on elytron and an anteriorly and posteriorly darkened pronotum; body slightly arched in lateral view. Elytron with fine punctation only, lacking large discal punctures. Colour: Upper side comparably dark; head yellowish or red, blackish or only slightly darkened anteriorly. Pronotum anteriorly and posteriorly dark, ferrugineous medially; elytron black with five yellow patches: two subbasal, two median, one apical (Fig. 2). The subbasal ones sometimes fuse and produce a subbasal band; the subbasal-submarginal patch reaches the margin of the elytron; the median-submarginal one is not in touch with lateral margin of elytron. Venter yellowish-ferrugineous, epipleuron yellowish anteriorly and ferrugineous medially; appendages yellowish to ferrugineous. © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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Sculpture: Head covered with polygonal meshes, medially densely punctate. Prono- tum densely punctate, some larger punctures visible basomedially; along anterior margin and laterally with microreticulation of polygonal meshes. Elytron with microreticulation consisting of slightly transversely orientated polygonal meshes; fine and densely punctate; the discal row of serial punctures comparably dense and well defined, 1st and 2nd lateral rows less distinct, an obsolescent sutural row visible. Male: Median lobe of aedeagus as in Fig. 6. Affinities: In colour rather strongly resembling N. moelleri HENDRICH & BALKE 1997 and N. pseudohydaticoides HENDRICH & BALKE 1997 from Sulawesi. From both it can be distinguished by its size and median lobe. Distribution: Neptosternus hydaticoides, as currently defined, is the most wide- spread species of the genus in SE Asia. It is distributed through the following countries: Indonesia [Lombok, Bali, Java, Sumatra], West Malaysia, Thailand, Vietnam, China [Hongkong, Guangxi], Taiwan and the Philippines, where the type material was also collected (Fig. 9). Habitat: The specimens from Palawan collected by Jan Kodada were obtained from a primary rainforest stream. Herbert Zettel collected specimens from vegetation at the edge of streams. In other SE Asian countries [e.g. West Malaysia: Pahang Province; Indonesia: Bali] N. hydaticoides is a common species and inhabits different stream and river types, in open pasture land as well as in forested areas, even in slightly polluted situations (HENDRICH & BALKE 1995).

Neptosternus montalbanensis sp. n. H o 1 o t y p e : S: "Montalbafsic!] Philippin.", "Staudinger Bang Haas", "Museum Paris 1945 Coll. R. Peschet" (MNHN). Etymology: Named after the type locality Montalban [Montalba], situated a few kilometres northeast of Manila (Luzon, Philippines). Description: Measurements (N = 1). Total length of holotype 3,00 mm; length without head 2,75 mm; greatest width of beetle 1,70 mm. Diagnosis: Small, somewhat broadly-elongate species with narrow subbasal band on elytron; body arched in lateral view. Elytron with fine punctation only, lacking large discal punctures. Colour: Upper side comparably dark; head ferrugineous. Pronotum ferrugineous ante- riorly and medially; slightly darker posteriorly. Elytron blackish with two yellow areas: a subbasal band; and a median-submarginal patch that is marginally fused with the apical patch (Fig. 3). Subbasal band and median-submarginal patch both reaching the margin of the elytron. Venter yellowish to castaneous brown, epipleuron yellowish anteriorly; appendages yellowish to ferrugineous. Sculpture: Head covered with polygonal meshes, medially with dense but fine punctation. Pronotum with dense but fine punctation, some larger punctures visible basomedially; along anterior margin and laterally with microreticulation of polygonal meshes. Elytron with microreticulation consisting of slightly transversely orientated polygonal meshes; fine and densely punctate; the discal row of serial punctures compa- rably dense and well defined, 1st and 2nd lateral rows less distinct, sutural row not present. © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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Male: Median lobe of aedeagus as in Fig. 7. Affinities: Neptosternus montalbanensis sp.n. resembles N. chumphon BALKE & HENDR1CH 1998 from Thailand (Figs 3, 4). However the latter species is smaller, more elongate and the body is only slightly arched in lateral view. The yellow patches on the elytra are more expanded. Furthermore the median lobe (Fig. 7) shorter than in N. chumphon (Fig. 8). Distribution: Philippines: Luzon. Only known from the type locality (Fig. 9). Habitat: Unknown. Most probably rheobiont, like other known species of the genus (e.g. HENDRICH & BALKE 1995).

A note on Biogeography

We have here mapped the currently known distribution of (S)E Asian Neptosternus (Fig. 9). Only one species of the genus occurs in Taiwan, which is not surprising, as this island appears to be the northern range limit of the Afrotropical-Oriental genus. In the Wallacea, the genus reaches as far east as Flores (only N. hydaticoides) and Sulawesi (10 species). The genus is not yet known to occur in the Moluccas. Neptosternus is rather speciose in SE Asia. There are 20 known species in mainland SE Asia, with a good part of these occuring in Vietnam (HENDRICH & BALKE 1997; BALKE et al. 1997). Nineteen species are known from Borneo, ten from Sulawesi and seven from the Sunda Arc islands. No or only one species are shared by two or more of these areas of endemism (Fig. 9, lines and "0" or "1" between the areas). This highlights the paucity of Neptosternus species on the Philippines, from where only three species are known. However, we suggest that it is still too early to speculate on the reasons for this enigmatic "lack" of species diversity. Rather, the Southern parts of the Philippines especially should be intensively searched for additional species, before the forests of even vaster areas are destroyed - taking their peculiar water beetle species with them.

Acknowledgements

We are indepted to Dr Manfred Jäch (Vienna, Austria) and Dr H. Perrin (Paris, France) for loan of the specimens and to Dr David Bilton (Plymouth, England) for critically reviewing the manuscript. This study was partially supported by the "Berlin-Forschung" and the "Studienstiftung des deut- schen Volkes".

Zusammenfassung

In der vorliegenden Arbeit werden zwei rheophile Schwimmkäferarten der Gattung Neptosternus von den Philippinen beschrieben: N. cebuensis von der Insel Cebu und N. montalbanensis aus der Umgebung von Manila [Luzon]. Zusammen mit N. hydaticoides sind damit drei Arten aus der Gattung von den Philippinen gemeldet. Neptosternus cebuensis ist dem N. biltoni aus Sulawesi sehr ähnlich, N. montalbanensis steht dem N © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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chiimphon aus Thailand sehr nahe. Die Diversität und die Verbreitung der Gattung auf den Philippinen werden dokumentiert und diskutiert, und anderen Regionen SUdostasiens vergleichend gegenübergestellt.

References

BALKE M., HENDRICH L. & CM. YANG (1997): Updating the Southeast Asian Neptosternus SHARP Fauna 1 (Coleoptera: Dytiscidae). — The Raffles Bulletin of Zoology 45(2): 369- 374. BALKE M. & L. HENDRICH (1998): Updating the Southeast Asian Neptosternus SHARP Fauna II (Coleoptera: Dytiscidae). — The Raffles Bulletin of Zoology 46(1): 135-138. HENDRICH L. &..M. BALKE (1995): Die Schwimmkäfer der Sundainsel Bali. Faunistik, Taxonomie, Ökologie, Besiedlungsgeschichte und Beschreibung von vier neuen Arten (Coleoptera: Dytiscidae). — Faunistische Abhandlungen des Museums für Tierkunde in Dresden 20(5): 29-56. HENDRICH L. & M. BALKE (1997): Taxonomische Revision der süostasiatischen Arten der Gattung Neptosternus SHARP 1882 (Coleoptera: Dytiscidae: ). — Koleopterologische Rundschau 67: 53-97. HENDRICH L. & M. BALKE (1999): Two new species of Neptosternus SHARP, 1882 from Southern India (Coleoptera: Dytiscidae). — Linzer biologische Beiträge 31(1): 57-62. REGIMBART M. (1877): Description de Dytiscides nouveaux de Manille. — Annales de la Society entomologique de France 7(5): 355-362. REGIMBART M. (1899): Revision des Dytiscidae de la region indo-sino-malaise. — Annales de la Society entomologique de France 68: 186-367.

Author's addresses: Lars HENDRICH Mörchinger Strasse 115 A D-14169 Berlin, Germany e-mail: [email protected]

Michael BALKE Evolutionsbiologie, Institut für Zoologie Freie Universität Berlin, Königin-Luise-Straße 1-3 D-14195 Berlin, Germany. e-mail: [email protected] © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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A/, cebuensis N. hydaticoides

3 X^/ 4 N. montalbanensis N. chumphon Figs. 1-4 - Habitus and coloration of Neptosternus spp. © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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5 \_/ 6 ^—/ 7 ^—' 8

A/, cebuensis N. hydaticoides N. montalbanensis N. chumphon

Figs. 5-8 - Median lobe of aedeagus (ventral view) of Neptosternus spp. © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

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O A. ^1 1 / ^^Philippines

Fig. 9 — SE Asian Neptosternus spp.. areas of endemism. species numbers, and faunal overlap between the areas (lines. "0", "1" = no or only one species shared); and distribution of Neptosternus in the Philippines: black dots = A', hydalicoides: black square = A1, montalbanensis; black diamond = N. cebuensis.